1. Field of the Invention
The present invention relates to an emulsifying or emulsified epoxy resin composition, a curable composition and processes for preparation thereof.
2. Description of the Related Art
Solvents have been employed to solve or dilute epoxy resins in the prior art. It is, however, well known that the regulation on the use of solvents has recently become stricter owing to the danger of fire from the solvents, the environmental problems resulting from air pollution from the solvents, the influences of solvents on the human body, the increase in the cost of solvents and so on.
A coating process using an aqueous epoxy resin has been used to solve the above problems. However, since epoxy resin emulsions, that is, aqueous epoxy resins, of the prior art contain an unreactive emulsifier in order to secure its emulsion stability, coating films formed from the epoxy resin emulsions are inferior to those formed with epoxy resins as such, or solutions thereof in solvents, with respect to their properties such as resistances to water and chemicals and film strength. On the other hand, when an emulsifier is selected so as to be able to maintain the properties of the coating film, it is difficult to emulsify an epoxy resin during the preparation of an epoxy resin emulsion.
U.S. Pat. No. 4608406 (published on Aug. 26, 1986; CELANESE CORP. and INTEREZ INC.) discloses a self-emulsification type epoxy resin prepared by modifying an epoxy resin. However, this epoxy resin has problems that the resin is poorly emulsifiable, the film formed by curing the resin exhibits poor film strength and the resin cures slowly.
Further, U.S. Pat. No. 4446256 (published on May 1, 1984; CELANESE CORP. and INTEREZ INC.) discloses a process for preparing a dispersant or an emulsifier for preparing aqueous epoxy resins which comprises reacting an aromatic, aromatic-originating or alicyclic diol with a diisocyanate and a long-chain aliphatic polyether glycol monoether, and U.S. Pat. No. 4987163 (published on Jan. 22, 1991; HOECHST AG) describes an aqueous disperse system, such as an emulsion or a suspension, comprising an epoxy resin prepared by dispersing or emulsifying a specific self-emulsification epoxy resin in water or a mixture of water with, if necessary, an organic solvent and/or additive. However, the preparations of these disperse or emulsion systems were not always easy in their dispersing or emulsifying step.